With an increase in the number of functions-per-chip, there is a corresponding increase in (1) the amount of bandwidth to be implemented and (2) the utilization of a high operational frequency for input/output (I/O) circuits. Also, it may be helpful to maintain low power budgets, low cost and low area for I/O circuits, especially for battery operated mobile devices. The high operational frequencies of the I/O circuits lead to fast rise and fall times of signals associated with the I/O circuits. At slow process corners (e.g., process, temperature and voltage parameters), the I/O circuits may be oversized so as to achieve high operational frequencies. However, at fast process corners, the high operational frequencies may lead to electro-magnetic induction (EMI), crosstalk, ringing, reflection, and/or power and ground bounce, which can degrade reliability of an I/O circuit. Process, temperature, and voltage (PTV) compensation may be utilized in certain circuits to tackle the above-mentioned issues. However, in the case of I/O circuits, the PTV compensation alone may not suffice, as the same I/O circuit may be used in different boards with different loading scenarios. Designing the I/O circuits for the worst case load scenario may lead to fast transition rates and EMI issues at low load scenarios.
In some exemplary scenarios, the above-mentioned issues may be mitigated by making a rise/fall time of an output signal of the I/O circuit programmable or load independent. However, making the rise/fall time programmable or load independent may lead to a compromise on performance, area and/or power. Further the achievable rise/fall time may be (1) rendered granular and (2) affected by a number of programming bits. Moreover, providing programmability within a few pre-defined levels of rise/fall time may not control EMI effectively due to the achievable rise/fall time being granular and affected by the number of programming bits. The achievable rise/fall time determines a slew rate of the I/O circuit. Several exemplary scenarios provide a slew rate compensation for a wide range of load values through miller feedback. However, miller feedback based techniques may negatively impact the performance and area of the I/O circuits. Also, several exemplary scenarios implement an external resistor for PTV compensation. However, using external resistors for PTV compensation can result in an increase in cost. Moreover, several exemplary scenarios use a common calibration for p-type metal oxide semiconductor (PMOS) and n-type metal oxide semiconductor (NMOS) based I/O circuits, and a specific calibration may not work with a skewed process. Furthermore, several exemplary scenarios are based on analog techniques that (1) are not suitable for low-power applications and (2) provide a low degree of programmability.